缺乏维生素D会显著增加患癌症的风险和死亡率

There are many reasons to be conscious of vitamin D. A reduced cancer risk is perhaps among the most notable, but compelling evidence also suggests optimizing your vitamin D can reduce your risk of death from any cause.

Researchers have also pointed out that increasing levels of vitamin D3 among the general population could prevent chronic diseases that claim nearly one million lives throughout the world each year.

Despite its name, vitamin D is not technically a vitamin. It's actually a steroid hormone that you get primarily from either sun exposure or supplementation, and its ability to influence genetic expression is thought to produce many of its wide-ranging health benefits.

Health Areas Benefited by Vitamin D

Many books could be written about the health benefits of vitamin D—far more than can be covered here—but to summarize in broad strokes, optimizing your vitamin D levels can help protect against:

According to longtime vitamin D researcher Dr. Michael Holick, research has shown that vitamin D deficiency can increase your risk of heart attack by 50 percent. If you have a heart attack and you're vitamin D deficient, your risk of dying from that heart attack is upwards of 100 percent.

Autoimmune diseases. Vitamin D is a potent immune modulator, making it very important for the prevention of autoimmune diseases, like multiple sclerosis1 (MS) and inflammatory bowel disease.

Lung disease. In those who are deficient, vitamin D supplementation may reduce flare-ups of chronic obstructive pulmonary disease (COPD) symptoms by more than 40 percent.2 Other research3 suggests vitamin D may protect against some of the adverse effects of smoking as well.

Infections, including influenza. Vitamin D also fights infections, including colds and the flu, as it regulates the expression of genes that influence your immune system to attack and destroy bacteria and viruses.

I believe it's far more prudent, safer, less expensive, and most importantly, far more effective to optimize your vitamin D levels than to get vaccinated against the flu.

DNA repair and metabolic processes. One of Dr. Holick's studies showed that healthy volunteers taking 2,000 IUs of vitamin D per day for a few months upregulated 291 different genes that control up to 80 different metabolic processes.

This included improving DNA repair; having a beneficial effect on autoxidation (oxidation that occurs in the presence of oxygen and /or UV radiation, which has implications for aging and cancer, for example); boosting the immune system; and many other biological processes.

According to one recent study6,7 seniors with low vitamin D levels may double their risk of dementia and Alzheimer's disease. Another study8,9,10 found that people with the highest average intakes of vitamin D had a 77 percent decreased risk for Alzheimer's.

Researchers believe that optimal vitamin D levels may enhance the amount of important chemicals in your brain and protect brain cells by increasing the effectiveness of the glial cells in nursing damaged neurons back to health.

Vitamin D may also exert some of its beneficial effects on your brain through its anti-inflammatory and immune-boosting properties.

Cancer. Vitamin D has a number of specific anticancer effects, including the promotion of cancer cell death, known as apoptosis, and the inhibition of angiogenesis (the growth of blood vessels that feed a tumor).

There are well over 800 references in the medical literature showing vitamin D's effectiveness against cancer. One recent meta-analysis11 concluded that vitamin D helps protect against bladder cancer. In all, having a high serum level of 25-hydroxyvitamin D was associated with a 25 percent reduction in relative risk of bladder cancer.

Similarly, a 2007 study published in the American Journal of Preventive Medicine12 concluded that a vitamin D level of more than 33 ng/mL was associated with a 50 percent lower risk of colorectal cancer.

Vitamin D for Breast Cancer

Breast cancer is the second leading cause of cancer death among American women,13 claiming the lives of nearly 40,000 women each year. While there are certainly many contributing factors, Carole Baggerly, founder ofGrassrootsHealth, believes that ordinary breast cancer may in fact be related to (or certainly exacerbated by) vitamin D deficiency.

It can also make a big difference in cancer recovery. Most recently, a meta-analysis of five studies published in the March 2014 issue of Anticancer Research14 found that patients diagnosed with breast cancer who had high vitamin D levels were twice as likely to survive compared to women with low levels.15,16,17

The analysis included more than 4,500 breast cancer patients over a nine-year period. The high serum group had an average vitamin D level of 30 nanograms per milliliter (ng/ml), which really isn't all that high as optimal is likely over 50 ng/ml.

Women in the low serum group averaged 17 ng/ml, which is the average vitamin D level found in American breast cancer patients.18 The researchers urge physicians to make vitamin D monitoring and optimization part of standard breast cancer care, and recommend that breast cancer patients should restore their vitamin D levels to a normal range of 30-80 ng/ml.

According to the featured findings, you need at least 30 ng/ml of serum 25-hydroxyvitamin D (25(OH)D) to prevent cancer from spreading. That said, other research suggests you may be better off with levels as high as 80 ng/ml.

Low Vitamin D May Be an Independent Risk Factor for Death

A robust and rapidly growing body of research clearly shows that vitamin D is critical for good health and disease prevention, in part due to the fact that it influences about 10 percent of all your genes.

Most recently, researchers used a technique called Mendelian randomization to assess the impact of vitamin D deficiency on health and overall mortality, and the results are compelling. As reported by the New York Times:19

"For the study,20 published in BMJ, researchers used data from Danish government health records on 95,766 subjects. All were tested for a genetic variant that reduces their vitamin D levels, and 35,334 also had their vitamin D serum levels measured...

By studying two large populations, of which one has the genetic variant for low vitamin D and the other does not, researchers were able to virtually eliminate the impact of confounding factors like other diseases, habits and behaviors that might be contributing to poor health. These traits would be evenly distributed in the populations studied, leaving only the genetic difference between them.

The scientists found that having the genes associated with lifelong low vitamin D increases the risk of cancer death by more than 40 percent and the risk of death from any cause by more than 30 percent. They found no effect on cardiovascular disease death. 'This study shows there may be a causal relationship' between vitamin D levels and death, said the lead author, Dr. Shoaib Afzal of Copenhagen University Hospital. But, he added, 'We can't recommend that you go out and buy supplements. We still need randomized trials for that.'"[Emphasis mine]

Contrary to Dr. Afzal's suggestion to hold off on the supplements, another recent report suggests children should be given free vitamin D supplements to address "a hidden epidemic of deficiency" that is driving disease statistics. The report21 was issued by the British National Institute for Health and Care Excellence (NICE). NICE also urges supermarkets to stock low-cost vitamin D supplements, and to promote them to high-risk groups, such as pregnant women, seniors, and people with darker complexion.

Sun Exposure Is the Ideal Way to Optimize Your Vitamin D Stores

If your circumstances don't allow you to access the sun, then taking a vitamin D supplement is certainly advisable. In this case, be sure to take vitamin D3—not synthetic D2—and take vitamin K2 and magnesium in conjunction with it. Vitamin D is fat soluble, so taking some form of healthy fat with it will also help optimize absorption. Vitamin A, zinc, and boron are other important cofactors that interact with vitamin D.

There are a number of important reasons for these recommendations. For starters, the biological role of vitamin K2 is to help move calcium into the proper areas in your body, and without sufficient amounts, calcium will build up in areas such as your arteries and soft tissues. This can cause calcification that can lead to hardening of your arteries—a side effect previously thought to be caused by vitamin D toxicity. We now know that inappropriate calcification is actually due more to lack of K2 than simply too much vitamin D.

Magnesium is also important, both for the proper function of calcium, and for the activity of vitamin D, as it converts vitamin D into its active form. Magnesium also activates enzyme activity that helps your body use the vitamin D. In fact, all enzymes that metabolize vitamin D require magnesium to work. As with vitamin D and K2, magnesium deficiency22 is very common, and if you're lacking in magnesium and take supplemental calcium, you may exacerbate the situation. Dietary sources of magnesium include sea vegetables, such as kelp, dulse, and nori. Vegetables can also be a good source. As for supplements, magnesium citrate and magnesium threonate are among the best.

How Much Vitamin D Is Required for Breast Cancer Prevention?

In 2011, a team of researchers led by Dr. Cedric F. Garland found that a vitamin D level of 50 ng/ml is associated with a 50 percent lower risk of breast cancer.23,24 At that time, they discovered that in order to achieve protective levels, you have to take far more supplemental vitamin D than previously thought.

To reach a minimum protective level of 40 ng/ml of vitamin D, study participants had to take anywhere from 1,000 IUs to as much as 8,000 IUs of vitamin D3 per day—a far cry from the recommended daily allowance of 600 IUs of vitamin D for adults. The supplemental dose ensuring that 97.5 percent of the study population achieved a serum 25(OH)D of at least 40 ng/mL was 9,600 IU/day. This study also concluded that intake of up to 40,000 IUs per day is unlikely to result in vitamin D toxicity.

GrassrootsHealth also has a helpful chart showing the average adult dose required to reach healthy vitamin D levels based upon your measured starting point. It's important to note, however, that it's virtually impossible to make a general recommendation on how much vitamin D to take as the amount needed can vary significantly from one individual to another. In essence, you need to regularly monitor your levels, and take whatever amount of vitamin D3 you need to maintain a clinically relevant level.

Finally, just in time for the new year, my team has come up with a helpful 2015 US vitamin D calendar. You can use it to track UVB levels by state throughout the year. Each month you can see how likely you are to obtain enough UVB rays based on where you live. The calendar is a $14.97 value but for a limited time, you can get it free with any order over $49.

How Vitamin D Performance Testing Can Help Optimize Your Health

A robust and growing body of research clearly shows that vitamin D is absolutely critical for good health and disease prevention. Vitamin D affects your DNA through vitamin D receptors (VDRs), which bind to specific locations of the human genome. Scientists have identified nearly 3,000 genes that are influenced by vitamin D levels, and vitamin D receptors have been found throughout the human body.

Is it any wonder then that no matter what disease or condition is investigated, vitamin D appears to play a crucial role? This is why I am so excited about the D*Action Project by GrassrootsHealth. It is showing how you can take action today on known science with a consensus of experts without waiting for institutional lethargy. It has shown how by combining the science of measurement (of vitamin D levels) with the personal choice of taking action and, the value of education about individual measures that one can truly be in charge of their own health.

In order to spread this health movement to more communities, the project needs your involvement. This was an ongoing campaign during the month of February, and will become an annual event.

To participate, simply purchase the D*Action Measurement Kit and follow the registration instructions included. (Please note that 100 percent of the proceeds from the kits go to fund the research project. I do not charge a single dime as a distributor of the test kits.)

As a participant, you agree to test your vitamin D levels twice a year during a five-year study, and share your health status to demonstrate the public health impact of this nutrient. There is a $65 fee every six months for your sponsorship of this research project, which includes a test kit to be used at home, and electronic reports on your ongoing progress. You will get a follow up email every six months reminding you "it's time for your next test and health survey."